In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis ...In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.展开更多
A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The...A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.展开更多
In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with p...In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with polyacrylic acid(PAA),TiO2 with polyethylene glycol(PEG 1000),and TiN,SiC,hydroxyapatite(noodle-like) with PEG 10000 to ammonia-water solution,respectively.The thermal conductivities were measured by using a KD2 Pro thermal properties analyzer.The influences of surfactant and ammonia on the dispersion stabilities of the binary nanofluids were investigated by the light absorbency ratio index methods.The results show that the type,content and size of nanoparticles,the temperature as well as the dispersion stability are the key parameters that affect the thermal conductivity of nanofluids.For the given nanoparticle material and the base fluid,the thermal conductivity ratio of the nanofluid to the ammonia-water liquid increases as the nanoparticle content and the temperature are increased,and the diameter of nanoparticle is decreased.Furthermore,the thermal conductivity ratio increases significantly by improving the stabilities of nanofluids,which is achieved by adding surfactants or performing the proper ammonia content in the fluid.展开更多
A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating ...A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.展开更多
Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhance...Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">By using a distillation tower as the regenerator, the coefficient of performance (COP) of the ammonia-water absorpti...<div style="text-align:justify;"> <span style="font-family:Verdana;">By using a distillation tower as the regenerator, the coefficient of performance (COP) of the ammonia-water absorption refrigeration cycle is calculated in </span><span style="font-family:Verdana;">this work. Two types of distillation towers, namely an equilibrium-stage</span><span style="font-family:Verdana;"> tower with a total condenser and a packed-bed tower with a partial condenser, are used in the cycle. From the simulation results, it is found that both types of distillation towers can successfully increase the COP of the cycle due to increased ammonia concentration in the vapor phase of the ammonia-water refrigerant. It was also found that the tower equipped with a partial condenser provides higher COP than that of the tower equipped with a total condenser. The value of COP can be further increased when the generator is replaced by the packed-bed tower in this water-ammonia absorption cycle. The effects of the mass flow rate ratio of NH</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O, stage number, reflux ratio and energy duty of the tower on the COP of the cycle are also studied in the present paper.</span> </div>展开更多
Absorption chillers are cooling units usually powered by renewable energy or waste heat.Their performance generally depends on the temperatures of the heat source,the ambient and the medium to be cooled.The present wo...Absorption chillers are cooling units usually powered by renewable energy or waste heat.Their performance generally depends on the temperatures of the heat source,the ambient and the medium to be cooled.The present work deals with the thermodynamic study of a 10 kW NH3/H2O absorption machine in order to find the COP(coefficient of performance).The first and second laws of thermodynamics were used for the operating conditions.The thermodynamic properties of the NH3/H2O mixture were determined using the EES(Engineering Equation Solver)software.The results of the simulation of the machine were validated with the results of the literature.After validation,the program was used to simulate a 10-kW NH3/H2O absorption machine for milk conservation/cold storage in northern Senegal.The simulation results of the 10-kW ammonia-water absorption machine give an acceptable COP of 0.521 with a milk storage temperature of 4°C.展开更多
This paper constructed a mathematical model of ammonia-water nanofluid falling film generation outside the vertical tube,which considers the change of the film thickness of the falling film solution,the thermal convec...This paper constructed a mathematical model of ammonia-water nanofluid falling film generation outside the vertical tube,which considers the change of the film thickness of the falling film solution,the thermal convection along the film thickness direction and the physical properties of the solution.By solving the mathematical model,the temperature field and other elements of the liquid film were determined.The influence of the properties of the working fluid on the heat and mass transfer in the falling film process is investigated.According to the calculation results,a method of adding nanoparticles in the process of ammonia falling film generation is proposed.The simulation results showed that the heat efficiency of entire falling film process can be enhanced by adding an appropriate amount of Al_(2)O_(3) nanoparticles.When the added Al_(2)O_(3) nanoparticles are 1 vol.%,the coefficient of the heat transfer is increased by about 4%,and the mass transfer effect is also improved by about 12%.In brief,the establishment of this model aims to improve heat and mass transfer efficiency and promote the application and integration of low-grade waste heat or renewable energy technologies in built environment.展开更多
The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used i...The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used in this ammonia-water based cycle. Energy analysis and parametric analysis are performed to guide the theoretical performance and experimental investigation is done to verify the theoretical results. The results show that the generator pressure, heating source temperature and turbine outlet depressurization made by the ejector can affect the cycle performances. Besides, the experimental thermal efficiency is much lower than the theoretical one on account of the heat losses and irreversibility. Moreover, the performance of liquid-gas ejector is affected by primary flow pressure and temperature.展开更多
This paper presents the importance and the cycle choice for long-distance transportation of low-grade thermal energy, and the thermodynamic and hydrodynamic feasibility of single-effect ammonia-water absorption system...This paper presents the importance and the cycle choice for long-distance transportation of low-grade thermal energy, and the thermodynamic and hydrodynamic feasibility of single-effect ammonia-water absorption system for heat or cold transportation over long distance are also involved. A model of a long-distance thermal energy transportation system is built and analyzed, which shows satisfactory and attractive results. When a steam heat source at 120℃ is available, the user site can get hot water output at about 55℃ with the thermal COP of about 0.6 and the electric COP of about 100 in winter, and cold water output at about 10℃ with the thermal COP of about 0.5 and the electric COP of 50 in summer. A small-size prototype is built to verify the performance analysis. Basically the experimental data show good accordance with the analysis results. The ammonia-water absorption system is a potential pro-spective solution for the heat or cold transportation over long distance.展开更多
特定堆型的一回路冷却剂中通过加入氨调控pH,并利用其辐解产物抑制氧化性物质的浓度,从而维持冷却剂的还原性状态。在此过程中,氨浓度与pH调控产生显著的联动影响,需要建立可模拟不同控制策略下水化学行为的模型,实现pH和溶解氢浓度控...特定堆型的一回路冷却剂中通过加入氨调控pH,并利用其辐解产物抑制氧化性物质的浓度,从而维持冷却剂的还原性状态。在此过程中,氨浓度与pH调控产生显著的联动影响,需要建立可模拟不同控制策略下水化学行为的模型,实现pH和溶解氢浓度控制。本工作基于RETA反应堆系统分析程序,开发了一个适用于压水堆型冷却剂辐解产物输运的模型,模型预测NH_(3)和H_(2)浓度与实验结果的均方误差分别为1.79×10^(−8)和5.69×10^(−8)。以KLT-40S堆型为对象,构建并对比分析了三种加氨调控策略:初始弥散加氨、源恒速加氨及基于除氢优化的源恒速加氨。在模拟过程中,设置了冷却剂初始参数与辐射场条件,逐步调整加氨速率与除氢时机。每种策略均模拟至系统达到准稳态(1.6×10^(4) s),以评估其对pH和溶解氢浓度的调控效果。结果显示,初始氨弥散策略简单直接,可维持体系的还原性但对冷却剂pH调控的时间小于5 h;源恒速加氨可长时间有效调节冷却剂pH,但会带来溶解氢浓度过高的问题,需匹配相应的除氢方案。采用基于除氢优化的源恒速加氨策略,能够同时满足稳定控制pH和溶解氢浓度的要求,加氨速率为1.64 g·s^(−1),加氨开始1200 s后开启除氢装置,除氢速率0.014 g·s^(−1),化学状态稳定后冷却剂的pH为6.9,溶解氢浓度为30~35 mL·kg−(1)(Standard Temperature and Pressure,STP)。本工作有望为新堆型研发和水化学控制策略的优化提供参考。展开更多
基金The National Natural Science Foundation of China(No.51176029)
文摘In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.
基金Project(50976022) supported by the National Natural Science Foundation of ChinaProject(BY2011155) supported by Science and Technology Innovation and Transformation of Achievements of Special Fund of Jiangsu Province, China
文摘A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.
基金Projects(51176029,50876020) supported by the National Natural Science Foundation of ChinaProject(2011BAJ03B00) supported by the 12th Five-Year National Science and Technology Support Key Program of China Project(ybjj1124) supported by the Foundation of Graduate School of Southeast University,China
文摘In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with polyacrylic acid(PAA),TiO2 with polyethylene glycol(PEG 1000),and TiN,SiC,hydroxyapatite(noodle-like) with PEG 10000 to ammonia-water solution,respectively.The thermal conductivities were measured by using a KD2 Pro thermal properties analyzer.The influences of surfactant and ammonia on the dispersion stabilities of the binary nanofluids were investigated by the light absorbency ratio index methods.The results show that the type,content and size of nanoparticles,the temperature as well as the dispersion stability are the key parameters that affect the thermal conductivity of nanofluids.For the given nanoparticle material and the base fluid,the thermal conductivity ratio of the nanofluid to the ammonia-water liquid increases as the nanoparticle content and the temperature are increased,and the diameter of nanoparticle is decreased.Furthermore,the thermal conductivity ratio increases significantly by improving the stabilities of nanofluids,which is achieved by adding surfactants or performing the proper ammonia content in the fluid.
文摘A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.
文摘Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">By using a distillation tower as the regenerator, the coefficient of performance (COP) of the ammonia-water absorption refrigeration cycle is calculated in </span><span style="font-family:Verdana;">this work. Two types of distillation towers, namely an equilibrium-stage</span><span style="font-family:Verdana;"> tower with a total condenser and a packed-bed tower with a partial condenser, are used in the cycle. From the simulation results, it is found that both types of distillation towers can successfully increase the COP of the cycle due to increased ammonia concentration in the vapor phase of the ammonia-water refrigerant. It was also found that the tower equipped with a partial condenser provides higher COP than that of the tower equipped with a total condenser. The value of COP can be further increased when the generator is replaced by the packed-bed tower in this water-ammonia absorption cycle. The effects of the mass flow rate ratio of NH</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O, stage number, reflux ratio and energy duty of the tower on the COP of the cycle are also studied in the present paper.</span> </div>
文摘Absorption chillers are cooling units usually powered by renewable energy or waste heat.Their performance generally depends on the temperatures of the heat source,the ambient and the medium to be cooled.The present work deals with the thermodynamic study of a 10 kW NH3/H2O absorption machine in order to find the COP(coefficient of performance).The first and second laws of thermodynamics were used for the operating conditions.The thermodynamic properties of the NH3/H2O mixture were determined using the EES(Engineering Equation Solver)software.The results of the simulation of the machine were validated with the results of the literature.After validation,the program was used to simulate a 10-kW NH3/H2O absorption machine for milk conservation/cold storage in northern Senegal.The simulation results of the 10-kW ammonia-water absorption machine give an acceptable COP of 0.521 with a milk storage temperature of 4°C.
基金Department of Science and Technology’s Natural Science Foundation(NO.BK20211386&NO.BK20211171)Jiangsu Market Supervisory Authority Scientific Research Project(KJ2022008)Key Laboratory of Low-grade Energy Utilization Technologies and Systems(Chongqing University),Ministry of Education of China(LLEUTS-202406)provided financial assistance for this creation of the article.
文摘This paper constructed a mathematical model of ammonia-water nanofluid falling film generation outside the vertical tube,which considers the change of the film thickness of the falling film solution,the thermal convection along the film thickness direction and the physical properties of the solution.By solving the mathematical model,the temperature field and other elements of the liquid film were determined.The influence of the properties of the working fluid on the heat and mass transfer in the falling film process is investigated.According to the calculation results,a method of adding nanoparticles in the process of ammonia falling film generation is proposed.The simulation results showed that the heat efficiency of entire falling film process can be enhanced by adding an appropriate amount of Al_(2)O_(3) nanoparticles.When the added Al_(2)O_(3) nanoparticles are 1 vol.%,the coefficient of the heat transfer is increased by about 4%,and the mass transfer effect is also improved by about 12%.In brief,the establishment of this model aims to improve heat and mass transfer efficiency and promote the application and integration of low-grade waste heat or renewable energy technologies in built environment.
基金supported by the National Natural Science Foundation of China (Grant No. 51076146)
文摘The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used in this ammonia-water based cycle. Energy analysis and parametric analysis are performed to guide the theoretical performance and experimental investigation is done to verify the theoretical results. The results show that the generator pressure, heating source temperature and turbine outlet depressurization made by the ejector can affect the cycle performances. Besides, the experimental thermal efficiency is much lower than the theoretical one on account of the heat losses and irreversibility. Moreover, the performance of liquid-gas ejector is affected by primary flow pressure and temperature.
基金Supported by Shanghai Municipal Science and Technology Committee (Grant No.06SR07106) in ChinaShanghai Pujiang Program (Grant No.06PJ14061) in China and Programme Interdisciplinaire Energie du CNRS-"VALOTHERM" in France
文摘This paper presents the importance and the cycle choice for long-distance transportation of low-grade thermal energy, and the thermodynamic and hydrodynamic feasibility of single-effect ammonia-water absorption system for heat or cold transportation over long distance are also involved. A model of a long-distance thermal energy transportation system is built and analyzed, which shows satisfactory and attractive results. When a steam heat source at 120℃ is available, the user site can get hot water output at about 55℃ with the thermal COP of about 0.6 and the electric COP of about 100 in winter, and cold water output at about 10℃ with the thermal COP of about 0.5 and the electric COP of 50 in summer. A small-size prototype is built to verify the performance analysis. Basically the experimental data show good accordance with the analysis results. The ammonia-water absorption system is a potential pro-spective solution for the heat or cold transportation over long distance.
文摘特定堆型的一回路冷却剂中通过加入氨调控pH,并利用其辐解产物抑制氧化性物质的浓度,从而维持冷却剂的还原性状态。在此过程中,氨浓度与pH调控产生显著的联动影响,需要建立可模拟不同控制策略下水化学行为的模型,实现pH和溶解氢浓度控制。本工作基于RETA反应堆系统分析程序,开发了一个适用于压水堆型冷却剂辐解产物输运的模型,模型预测NH_(3)和H_(2)浓度与实验结果的均方误差分别为1.79×10^(−8)和5.69×10^(−8)。以KLT-40S堆型为对象,构建并对比分析了三种加氨调控策略:初始弥散加氨、源恒速加氨及基于除氢优化的源恒速加氨。在模拟过程中,设置了冷却剂初始参数与辐射场条件,逐步调整加氨速率与除氢时机。每种策略均模拟至系统达到准稳态(1.6×10^(4) s),以评估其对pH和溶解氢浓度的调控效果。结果显示,初始氨弥散策略简单直接,可维持体系的还原性但对冷却剂pH调控的时间小于5 h;源恒速加氨可长时间有效调节冷却剂pH,但会带来溶解氢浓度过高的问题,需匹配相应的除氢方案。采用基于除氢优化的源恒速加氨策略,能够同时满足稳定控制pH和溶解氢浓度的要求,加氨速率为1.64 g·s^(−1),加氨开始1200 s后开启除氢装置,除氢速率0.014 g·s^(−1),化学状态稳定后冷却剂的pH为6.9,溶解氢浓度为30~35 mL·kg−(1)(Standard Temperature and Pressure,STP)。本工作有望为新堆型研发和水化学控制策略的优化提供参考。
